Oscillator devices are commonly used to generate periodic signals having a certain frequency. Such periodic signals may for example be used as clock signals, for example, for clocking a digital logic. In other examples, such periodic signals may be used as carrier signals for data communication.
For example, in integrated circuits (ICs), e.g., system ICs, for automotive or industrial applications integrated oscillators are used for supplying a digital logic and/or for supplying communication devices. For such communication devices, for example, a controller area network (CAN)-interfaces, it is necessary to generate a precise clock signal having a high frequency, for example, of the order of 80 MHz, although other frequencies may be required as well, e.g., in other applications. In some applications, frequency variations of a signal generated by the oscillator device have to be minimized, for example, limited to a range of ±1%, although other accuracies may also be required. On the other hand, for many applications it is desirable to keep a power consumption of the oscillator device low, to have a low start-up time of the oscillator device, and/or to minimize a chip area required for the oscillator device.
In some conventional oscillator devices, frequency dependent resistors may be used in a control loop. However, in some conventional approaches the use of a frequency dependent resistor may cause sawtooth-like signals, which requires filtering. Such filtering may in some cases require considerable chip area and/or may make achieving low start-up times difficult.
In the following, illustrative embodiments will be described with reference to the attached drawings. It is to be noted that these embodiments serve illustrative purposes only and are not to be construed as limiting the scope of the present application. For example, while embodiments may be described as comprising a plurality of elements, in other embodiments some of these elements may be omitted and/or replaced by alternative elements. In still other embodiments, additional elements may be provided. Furthermore, elements from different embodiments may be combined with each other to form additional embodiments unless specifically noted otherwise.